1. Field of the Invention
The present invention generally relates to software programs that simulate the physical structures that will be produced by manufacturing processes, and more particularly to an improved method and system that correlates the software results to actual hardware devices produced.
2. Description of the Related Art
A major element in the qualification of any new semiconductor technology, circuit element, or product is a model to hardware correlation (MHC). An MHC is an exhaustive process that involves comparing a software based simulation of several devices (e.g., circuits) with the hardware performance of the same device or circuit. This activity allows circuit designers, technology developers and EDA (Electronic Design Automation) tools developers to find any mismatch between the technology specifications and the end product delivered from the manufacturing facility. Any mismatch is addressed and a further MHC is pursued to verify the solution.
An MHC is fairly simple if all the process parameters are run at exactly nominal conditions. However, the manufacturing line only guarantees that each parametric parameter will be in a certain range. The overall range of all of these parameters is called the “Process Window”. Often qualification engineers wish to evaluate the MHC at corners of the Process Window that are artificially skewed away from nominal conditions. For example, several lots of test sites may be run with artificially long channel lengths to evaluate if the device model is still accurate in case the manufacturing line allows channel length to run a bit too long. In order to perform an MHC on this hardware, the artificially long channel length must be accounted for in the software simulation.
One of the main conventional processes to evaluate MHC is a Best Case/Worst Case Analysis. This allows designers to see the overall margin in their designs by simulating best and worst case hardware, and comparing to the fastest and slowest hardware that the manufacturing line would deliver to a customer. The problem with this analysis is it simply reflects if the amount of bounding in simulation is adequate for the process variations in manufacturing. This type of analysis does not pinpoint individual process parameters and their effect on circuit performance.
Therefore, the invention allows for the incorporation of device (semiconductor chip) specific parametric data into a circuit simulation. The simulation can be tailored to reflect the performance and behavior of a specific device, by running several device-specific simulations of this type and comparing the results to the respective devices, one ordinarily skilled in the art can accurately pinpoint the circuit sensitivities to individual process parameters. The MHC attempts to match the behavior and performance of the specific devices, instead of bounding the timing with Best Case/Worst Case analysis.
This invention also allows the qualification engineer to model the effects of several manufacturing process variations which have not been accurately modeled. Further, the invention allows for the accurate incorporation of threshold voltage adjustment implant variation into the circuit simulation by way of an iterative simulation methodology. Presently there exists no way to accurately incorporate the true threshold voltage of a device specific simulation.